This invention relates to filling material composed of synthetic fibers for use in coats, gloves, bedclothes, and the like, and to a process for manufacturing such filling material.
Various kinds of natural or synthetic filling material are known. Natural feather or down, e.g. from water fowl, is an excellent filling material having a number of outstanding properties, including bulkiness, good heat insulation, softness, resiliency, moisture absorption and permeation. Natural feather or down has, however, several disadvantages. For example, a lot of steps are required for processing natural feather or down, since it is highly susceptible to damage by insects and microorganisms. Natural feather and down is also expensive, since it is available only in limited quantities. Further, very fine powdery fragments of down or feathers are likely to induce an allergic reaction. These and other problems have prompted research on novel fibrous materials to develop substitutes for natural feather or down. It has, for example, been proposed to manufacture downlike material by bonding filaments into bundles and cutting them, as taught in Japanese Patent Publication No. 7955/1973; to partially bundle and bond short fibers as taught in Japanese Utility Model Publication No. 27227/1969; to form fibers into a spherical shape as taught in Japanese Patent Publication No. 39134/1976; and to flock fibers by electrodeposition as taught in Japanese Patent Publication No. 17344/1972. It has also been proposed, in Japanese Patent Publication No. 305/1970 to manufacture featherlike material by bonding parallel bundles of fibers with adhesive fibers. No such downlike or featherlike material is, however, commercially available, apparently because no material that is comparable to natural material in physical properties has heretofore been obtained. It is, for example, very difficult to prepare down artificially, since natural down is composed of 20 to 200 barbs grown from a rachis, and having a length of 3 to 30 mm with an average length of 14 mm, and one or two barbules grown on each barb for every 100 microns of its length. Moreover, down substitutes are considered difficult to manufacture continuously at a low cost. For example, in the process for manufacturing filling material by bonding a bundle of filaments by adhesion or melt adhesion intermittently along the length thereof, cutting the bundle into a plurality of masses, and opening the filaments, it is very difficult to bond the filaments in the center of the bundle, or even virtually impossible to do so if the filaments have a high total denier. Also, the adhesion of filaments to each other is likely to occur in lines along the length thereof. It is very difficult to open those filaments, and obtain therefrom filling material having the desired high degree of thermal insulation and bulkiness. For example, the filling material obtained at an opening rate of, say, 10% has only a bulkiness of, say, 30 cm/g. It is definitely inferior to natural feather or down, and of low commercial value even if it is used for filling a guilt or mattress. If the opening of fibers is insufficient, the bundles of fibers have difficulty in moving individually in the filling material, and are likely to get entangled together forming a ball in a guilt. Therefore, it is impossible to obtain filling material which is comparable to natural feather or down. The process which forms fibers into a spherical shape, the process which employs flocking by electrodeposition, and the process for manufacturing featherlike filling material by bonding parallel bundles of fibers with adhesive fibers are all complicated, and low in productivity. The process which bundles and partially bonds short fibers has the disadvantage that it does not lend itself to continuous mass-production. Down-like cut fibers having coiled crimps, and mixtures of down with such fibers are already commercially available. These products, however, differ from natural down in structure, and have only two-dimensional structure. Moreover, such fibers are long, and likely to form balls.
The present invention results from extensive research which was undertaken to develop a process for the industrial manufacture of filling material which is similar to natural feather or down (particularly down) in both structure and physical properties.